"I've got a $20 bet he shows up," Bush said during a town hall with employees of Nationwide insurance at the company's headquarters here Wednesday afternoon.

Asked by reporters after the event why he thinks Trump might go back on his promise to skip the seventh Republican debate, Bush said, "Because it's in his interest."

Bush, who has tried in recent weeks to assert himself as the Republican most willing to criticize Trump, laughed off Trump's stated reason for skipping the Fox News Channel debate: his complaint that the network, and specifically co-moderator Megyn Kelly, hasn't treated him fairly.

"Really? He complains about not being treated fairly by the press? He consumes all the press," Bush said. "He's a Stradivarius violinist in the Vienna symphony, man. I mean, the press is just being played like nobody's business.

"Poor little Donald," Bush continued. "Barack Obama doesn't go on Fox either, so now they have that in common."

Bush's campaign has struggled for months to gain a foothold in a topsy-turvy primary cycle that has been dominated by the brash billionaire and his ability to earn free media and drive the overarching narrative about the GOP's nomination battle.

Polls now show Trump with a slight lead in Iowa, with five days to go until Monday night's caucuses.

Bush, who is focused more on a strong showing in New Hampshire's first-in-the-nation primary on Feb. 9, has never pulled up stakes in Iowa, although he is not campaigning like a candidate who has to finish strong here.

Wednesday's 70-minute town hall was his first Iowa event of caucus week, and Bush is scheduled to campaign across the state over the weekend.

Fighting a cold after his Tuesday trip to Elko, Nev., Bush was his normal, wonky self during his town hall, offering long, expansive answers to questions on a number of subjects. His comments about Trump went on for six minutes; and he spoke for nearly five minutes in response to a question about protecting the nation's water supply.